1. Field of the Invention
The present invention relates to a disk array device including a hot spare disk thereby to achieve higher reliability, an operating method of the disk array device and a program-storing medium.
2. Description of the Related Art
Generally, a hot spare disk in a disk array device is in a standby state until a disk comprising RAID (Redundant Array of Inexpensive Disks) fails, and once the disk in operation fails, the disk is replaced with the hot spare disk.
In addition, there is provided a disk array device as a related art of the present invention which performs periodic replacement of each disk with a hot spare disk based on the current-carrying time of the disk. In other words, a disk controller controls the current-carrying time of each disk so that a disk including the longest current-carrying time is replaced with a hot spare disk (see patent document 1: Japanese Patent Laid-open Publication No. 2000-293315, for example).
Further, there is another related art of the present invention which utilizes equalization of cumulative rotation times of respective magnetic disks (see patent document 2: Japanese Patent Laid-open Publication No. 8-190762, for example).
Next description is made about problems of the above-mentioned related arts.
First, in the above-mentioned typical disk array device, it is not until there occurs a trouble that an operating disk is replaced, so there is a problem that the RAID redundancy is reduced or becomes lost between the time when the trouble arises and the time when the replacement is finished.
There is another problem that a hot spare disk remains in the standby state and still new even though only a hard disk comprising RAID is operated for a longer time and its failure probability becomes higher.
Further, as the disk array devices disclosed in the above-mentioned patent documents 1 and 2 do not consider a variety of failure probabilities among disks based on the individual specificity such as hard disk manufacturer, model number or the like, if the individual specificity is largely different between a failure-prone disk and a failure-proof disk, the hard disk with shorter current-carrying time or shorter cumulative rotation time may fail earlier than the hard disk with longer current-carrying time or longer cumulative rotation time. This may finally reduce the effect of decreasing the failure probability of the disk array device as a whole.